[ClusterLabs] Updating quorum configuration without restarting cluster

[Jan Friesse]

Gerry,

> Dear community,
> 
> I would like to ask few questions regarding Corosync/Pacemaker quorum configuration.
> 
> When updating the Corosync's quorum configuration I added last_man_standing, and
> auto_tie_breaker in corosync.conf on all hosts and refreshed with
> 'corosync-cfgtool -R'.
> Note that that man page included with the rpm says that the -R option with "Tell
> all instances of corosync in this cluster to reload corosync.conf."
> 
> Next I run 'corosync-quorumtool -s', but it did not show the new quorum flags
> for auto tiebreaker and last man standing.
> 
> Once I restarted the corosync cluster, the auto tiebreaker flags and last man
> standing flags appeared in the corosync-quorumtool output as I expected.
> 
> So my questions are:
> 1. Does corosync-quorumtool actually shows the active quorum configuration? If
> not how can I query the active quorum config?

Yes, corosync-quorumtool shows quorum configuration which is really used 
(it's actually only source of truth, cmap is not).

> 
> 2. Is it possible to update the quorum configuration without restarting the cluster?

Partly.

Basically only quorum.two_node and quorum.expected_votes are changeable 
during runtime. Other options like:
- quorum.allow_downscale
- quorum.wait_for_all
- quorum.last_man_standing
- quorum.auto_tie_breaker
- quorum.auto_tie_breaker_node

are not (wait_for_all is a little bit more complicated - when not 
explicitly set/unset it follows two_node so it is possible, but only in 
this special case, to change it via changing two_node).

Regards,
   Honza

btw. I've already replied to Janghyuk Boo so mostly copying same answer 
also here.

> 
> Thank you,
> Gerry Sommerville
> E-mail: gerry at ca.ibm.com <mailto:gerry at ca.ibm.com>
> 
> 
> 
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